Pulse time telemetric system



April l20, 1954 M WALLACE PULSE TIME TELEMETRIC SYSTEM 2, Sheets-Sheet 1 Filed June 16. 1947 Sme/Mon MARCEL WALLACE @www April 2o, 1954 M. WALLACE 2,676,316 PULSE TIME TELEMETRIC SYSTEM F'iled June 16, 1947 2 Sheets-Sheet 2 T0 RECEIVER 9| SPEED STEP DOWN 'GEARING MARCEL WALLACE www Patented Apr. 20, 1954 PULSE TIME TELEMETRIC SYSTEM Marcel Wallace, East Port Chester, Conn., as-

signor, by mesne assignments, of one-half to said Wallace, doing business as Panoramic Laboratories, East Port Chester, Application June 16,

24 Claims. 1

This application is a continuation-impart of applications for U. S. Patent No. 633,138 Iiled in the names of Wallace and Wu on December 6, 1945 now U. S. Patent 2,505,314 and of an application for U. S. patent entitled Telemetric Pulse Time Position Recorder led in the name of M. Wallace on April 25, 1947 and identifiable as Serial No. 743,939, now U. S. Patent 2,534,841 and of a further application for U. S. patent entitled Altitude and Distance Recorder, tiled in the name of M. Wallace concurrently with the present application, as Serial No. 754,941, now United States Patent #2,609,532, and of a further application for U. S. patent entitled Frequency and Pulse Time Modulation Telemetric System and filed concurrently herewith in the name of M. Wal-- lace and identified as Serial No. 754,940.

The present invention relates generally to telemetric devices which are operative to transmit` the values of a plurality of measurable quantities from each of one or more measuring and transmitting locations, in terms of pulse time position modulations of pulses which are in any event transmitted for purposes of distance measuring by means of radar equipments of the type which measure transmission times of radiant energy pulses as a measure of distance.

In the application for patent led in the name of Wallace and Wu, referred to hereinbefore is disclosed a method and a system for transmitting pulses timed with respect to an arbitrary zero of time in accordance with a measurement of altitude, and a method and a system for interpreting the timing of the pulses at a remote location, and there indicating the values of altitude. While altitude representative transmissions are provided in the system, as disciosed, quite obviously the principles of the system are applicable to the transmission of values of any measurable quantity which may be translatable4 into an angular position of a pointer.

In my application for U. S. patent entitled Telemetric Pulse Time Recorder, and led concurrently herewith, I disclose how a system of the general type disclosed in the Wallace-Wu application may be utilized in conjunction with a facsimile type recorder of a plurality of measurable quantities, these values being transmitted from random locations as pulse time position modulations.

In my application for Altitude and Distance Recorder, le-d concurrently herewith, I show how the normal pulse type distance measuring equipment may be adapted for telemetric recording in accordance with the principles of my invention in Telemetric Pulse Time Position Recorder.

In my application -for U. S. patent entitled Frequency and Pulse Time Modulation Telemetric, System, and filed concurrently herewith,

for recording the values.

Conn.

1947, Serial No. 754,828

I have shown how a recording of telemetric information of one character may be superimposed on a. recording of telexnetric information of another character, by utilization of the fact 5 that in facsimile type recorders are normally provided two distinct time parameters, one represented by lateral scan of a record receiving surface and the other by timed feeding of the said surface. Specifically, and as one mode of application of the invention I telemetrically transmit altitudes of aircraft in terms of transmitted frequencies, which are recorded in a line extending generally longitudinally of a record receiving surface, and instantaneous values or altitudes being meaesured by the lateral positions of the recorded lines, and I superimpose modulations on the recorded lines at longitudinal positions representative of other quantities, such as range or azimuth, or both.

In the present application I improve the system disclosed in my application for U. S. patent entitled Altitude and Distance Recorder wherein substantially continuous recordings of the value of a measurable quantity are provided at lateral positions of a record receiving surface in accordance with pulse time position modulations, the pulses being utilized in measuring distance, in any event, by introducing into the system the principles of myv application for U. S. patent entitled Frequency and Pulse Time Modulation Telemetric Systei by superimposing on the record, longitudinally positioned modulations thereof, which represent in terms of their longitudinal positions the values of measurable ci' quantities.

Broadly described, the present invention involves a pulse type radiant energy transmitter and receiver, which are utilized in conventional fashion for distance measuring by providing in conjunction therewith circuits and apparatus for measuring time elapse between pulse transmissions and pulse receptions, the elapse occurring by reason of time consumed by the radiant energy in traveling to a radio beacon, repeater or transponder, and to return to the receiver. Systems of the above briefly described character are well known under the descriptive style and name of Radan and require no extensive elucidation in the present application.

In distance measuring systems which operate on the principle of measuring travel time of pulses of electro-magnetic energy tc a reilecting or transponding location and back to the source of energy, the precise times of occurrence oi the transmitted pulses has not normally been matter of importance, since only the time elapse between transmission and receptions has had signiiicance in determining range or distance. In systems wherein a largeV number of measuring equipments of the pulse type have operated on the same or closely adjacent frequencies, and in a relatively restricted area, it has in fact become the conventional practice to transmit trom each oi the equipments at random, to avoid or to minimize the possibility of interference between distinct equipments.

At the present time a type of distance measuring system which has received the approval oi the Civil .Aeronautics Authority, for determining the distance of airerat from a transponder or repeater station located at an airport or other fixed location, provides for the transmission from each of a plurality of aircraft of pulses at random times and with random spacings, both with respect to the transmissions from any one aircraft, and with respect to the transmissions from the various aircraft considered as a group. The reason for the random character of the trans-- missions is, as has hereinbefore been indicated, to avoid or to minimize the possibility of interference between measuring equipments, all of which receive signals from the same transponder. The receiver of each of the distance measuring equipments is gated to enable reception of'pulses only during times after pulse transmissions which correspond to the range which the equipment is momentarily measuring. By causing the average time between transmitted pulses in a given equipment to be large relative to the time thereceiver o that equipment is gated open, the majority of pulses transmitted from adjacent equipments are not eective with respect to the given equipment, and those which do escape past the time gate, due to their random occurrence, have negligible eiiect on the range measurement. ,o

It is my conception that the times or time positions of transmission of pulses emitted by the pulse type distance measuring equipment above briefly described, may be controlled in accordance with the value of a measurable quantity, without destroying, or, in fact, affecting in any way, the advantages and mode of performance of the distance measuring equipment. The time positions of the emitted pulses from any desired number of pulse transmitters may be translated at an indicating or recording station, remote from the several pulse transmitters, in terms oi the values or" the measurable quantity, providing at the station continuous indications, in transient or permanent form, of the values of the quantity.

More specifically, I desire to apply my invention to the transmission of altitude information from a plurality of aircraft, by means oi time position modulation of the pulses which are transmitted by the craft in the process of obtaining distance measurements.

In order to make eiective application of a system of pulse timing modulation for telemetric purposes, a reference time must be provided, as well as a reference time scale, which are common to the entire system, so that the time positions of pulses transmitted by various transmitters to represent various telemetric values, shall be translatable or interpretable in terms of a common reference time and time scale. Since it is expected that substantially all airports will, in the course of time, and in accordance with the requirements of the Civil Aeronautics Authority, be provided with omni-directional beacon systems, and since such systems provide transmissions at a iixed frequency and at a constant phase, I prefer to utilize these transmissions to provide the required time scale, as well as the required zeros of time. It will be understood, however, that such utilization of transmissions which are in any event available, involves merely a matter of convenience, and that a time scale and zero time references for the system of the invention may be provided in other ways.

I have discussed hereinbefore the concept o limpressed time position modulations on pulses which are transmitted in any event for the purpose of making distance measurements. The function of translating or interpreting 'the modulated pulses may be accomplished by means of a line scanning recorder, of 'the type now quite common andv well known in connection with facsimile recording, and having a helical platen which scans, by virtue oi a r tary motion imparted thereto, laterally of Ya timeded record receiving surface, in synchrcnism with the pulse transmissions, each possible time position of the transmitted pulses bearing a deiinite and invariable correspondence with a recording position on a line extending laterally across the record receiving surface.

It will be realized, when the inode of operation of the now conventional line scanning facsimile type recorder is considered, that two time'representative axes or references are provided thereby. The first represents a lateral scan of a record receiving surface, which I propose to utilize `for measuring altitude, although obviously any other quantity might be teleinetrically recorded in place oi altitude without departing from the spirit of the invention. The second airis or reference is the longitudinal motion or feed o the record receiving surface past the line scanning mechanism.

I provide on the record receiving surface successive zero time markers, the time elapse between which is representative of a measuring cycle devoted to the determination of times ci modulation oi the pulse time positions of the transmitted pulses, either by omitting pulses or series of pulses r by displacing the times of pulses or series ci pulses. The times of occurrence of the modulations oi pulse time positions which are representative of a rst quantity may be controlled in accordance with values of further quantities, and the values of these quantities may be read on the record of values of the first quantity by measuring the locations of modulations of the record produced thereby. By this means I may provide for the transmissions oi the values of a considerable number of distinct quantities by timing of pulse positions, without time sharing or time division multiplexing, and I provide for recording of the values by means of a relatively simple facsimile type recordingapparatus, which requires but slight modiiication to adapt it to the present system.l At the same time the system of the present invention does not interfere in any deleterious manner with the normal function and operation of the distance measuring equipment which is utilized for generating the modulated pulses.

Accordingly, it is an object of the present invention to provide a telemetric system o the type utilizing pulse time modulation.

It is a further object of the invention to provide an improved pulse type distance measuring system, wherein the time positions of pulses otherwise transmitted for the purpose of measuring distance provide a measure of the value of a measurable quantity, and wherein the transmitted pulses may be further modulated in accordialce with the value of a further measurable quan- It still a further object of the present invention to provide an improved pulse type distance measuring equipment wherein thev timing of transmitted pulses is controlled in accordance with the value of a measurable quantity, and wherein the said pulses are subjected to modulation at timed intervals determined in accorde ance with one or more further quantities.

It is another object of the present invention to provide a telemetric recording system for recording laterally of time fed receiving surface timepositions of transmitted pulses, and wherein longitudinal modulations of thelateral record are provided to represent the values of further quantities.

It is a further object of the present invention to provide a pulse type distance measuring equipment modied to cooperate with a telemetric recorder, without deleterious eiect to the normal function of the equipment, by controlling the time position of each transmitted pulse inaccordance with values of a iirst meausrable quantity, and by modulating certain only of the transmitted pulses selected in accordance with the values 0f one or more further measurable quantities.

More speciiically stated, it is an object of the present invention to provide a system of pulse type distance measuring equipments, each located on a diiierent elevated object, and all operating in conjunction with a single and the same radar beacon or transponder to determine range with respect thereto, and wherein the timing of the transmitted pulses from each of the equipments is determined with respect to an arbitrarily determined zero of time and a time scale, common to the entire system, in accordance with the altitude of the associated elevated object, and wherein, further, certain pulses are selected for modulation or timing deviation in accordance with the value of the range or the azimuth of the object, or both, which determine times measured with respect to a further arbitrary zero of time, and a time scale, common to the entire system.

It is an object of the invention, further, in conjunction with the last mentioned object, to provide a central recorder for recording altitudes of the various objects in terms of lateral positions of longitudinally extending time records, individual to the various craft, and for recording the values of range, or azimuth, or both in terms of modulations or temporary lateral deviations of the time records, at longitudinal positions along the time records corresponding with the measured values of range, or azimuth, or both, time scales being established for lateral scanning of a record receiving surface and for time feeding thereof, in precise correspondence with the. time scales utilized. in determining pulse timey positions representative of altitude, and modulation times representative of azimuth, or range, or both.

The above and still further objects, advantages and features of the present invention will become evident upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

Figure l is a circuit diagram, and a conventionalized mechanical drawing, partly schematic and partly in functional blocks, of apparatus required at' each telemetric transmitting station, in the system of the present invention;

Figure 2 is a circuit diagram, in functional block diagram, together with a conventionalized showing `of a facsimile type recorder, in accordance withthe invention;

` puiser 2, and apply to Figure 3' is a plan view of a record receiving surface having. thereon records provided' in accordance with the invention;

Figure 4 is' a view in elevation of av zero-setting or framing mechanism utilized in the practice of theinvention.`

Referring now more specically to the drawings, the reference numeral l denotes a radio transmitter, which operates at any convenient and constant frequency, say mc., for purposes of example, The transmitter I is associated with a puiser 2, which serves to energize the transmitter IV to transmit short pulses or bursts of radio frequency energy in response to each control pulse applied to the puiser. Control pulses forV the pulser 2 are developed by means of an equipment of the typev disclosed in the aforementioned application for U. S. patent, Serial No. 633,188, nled on December 6, 1945, in the names of Wallace and Wu, and comprises an altimeter 3 of the aneroid cell type which serves to position an angu-larly positionable pointer 4, about a pivot 5, causing the pointer 4 to assume an angular position corresponding with and determined by the altitude measured by the altimeter 3'. Secured to the pointer d in any convenient fashion is a small permanent magnet 6. A synchrcnous motor l drives a shaft il, which is aligned with the pivot 5, and to which is secured an arm Sc having at one end a pick-up coil 9, which is rotated as the shaft 8 and arm 8a turn, in a path immediately adjacent the locus of possible positions of the magnet 6. Upon each passage of the pick-up coil e past the magnet 6 there is induced in the coil 9 a voltage, by virtue of the operation oi Faradays law. This voltage is conveyed by means of lead it from the coil 9 to a slip ring Il secured to the shaft 8, and thence to a brush I2, leads from which extend` to the the puiser 2 for control purposes the voltages induced in the coil 9.

The 'equipment and apparatus described in the altimeter 3 and hence upon altitude.

We may assume that a plurality of the altitude timed pulse transmitters hereinafter. Under such aircraft will transmit peri-- each of a plurality of air- -also be recorded in permanent forni on a aircraft carrier, and wherein the time required for transmission of the pulses to the transponder and back to a receiver associated with the transmitter is measured to determine range. It has been explained that the random character of the transmitted pulses is enforced for the purpose of minimizing interference between aircraft which are transmitting and receiving contemporaneously. While this random operation of the distance measuring equipment has been considered essential heretofore, it is rather nonsimultaneous transmissions which are essential, and these may be provided as among a plurality of transmitters by what may be described as an ordered randomness, as distinguishable from a purely chance randomness, without loss of any of the benefits of the latter.

More specifically I propose initter i as the interrogator of a pulse type distance measuring equipment, which is in essence merely an interrogator-responsor. Thereby each aircraft is constrained. to transmit pulses at the saine repetition rate, out at time positions corresponding with altitude, so that aircraft flying at even slightly distinct and different altitudes are incapable of simultaneous transmissions. An ordered randsomness is introduced into the transmissions of the interrogatcrsV of the distance measuring equipment Which serves to prevent interference between transmissions from distinct aircraft with the same Veffectiveness as has been the case hitherto by transmission at chance random.

The control of pulse timing in the interrogators of the present system in accordance with the value of a variable parameter, for example altitude, `enables determination at remote stations 'of the values of said parameter as associated with each of the transmitting aircraft, and in accordance with the principles and apparatus disclosed in. co--pending application of lfl. Wallace, Serial No. 743,949, filed April 25, 1947, and entitled Telenietric Pulse Iliine Position Recorder, of which this application is a continuation-in-part, the values ofV said parameter may time fed and time calibrated record receiving surface or strip.

Disregarding for the immediate present the distance measuring function of the airborne equipment of thepresent system, and turning our attention to the ground recording` station. there is provided a pulse receiver 3G, arranged to receive and dernodulate pulse signals of the character of those transmitted by the airborne transmitters or interrogators of the system. Detected pulses provided by the receiver 3i) are applied, after amplication, if required, to the marker electrode 3l of a facsimile type recorder 32, having a helical platen 33 and a time fed record receiving surface til. The specific character and structure of the recorder 3T. .forms no port of the present invention, and 'l may utilize various recorders of the type indicated, such recorders being available for purchase corninercially and having been the subject of the grant of a considerable number of Letters Patent of the United States. specify, however, that a recorder of the type disclosed in U. S. Patent #2,215,806, issued to C. J. Young and dated September 2li, 194i), is satisfactory for the purpose in hand,r and male reference to that patent for a full and complete disclosure of a suitable recording mechanism. Suffice itY to state in the to utilize the transpresent application, that marks are created on the surface 34 upon application tothe marker tl of a suificient voltage, the lateral position of the mark being determined by the instantaneous position of the helical platen at the instant of application of the said voltage. The platen 33 of the recorder 32 is rotated by means of a synchronous motor 35 at the same speed and with the same framing phase as are the various synchronous motors 1, located at the telemetric transmitters of the system, and which cause rotation of pulse generating pick-up coils 9. In order to assure that the synchronous motor 35 and the various synchronous motors l shall be synchronised and identically framed, the motor 35 is utilized to control a sync signal generator 35, which supplies its output to a radio transmitter 31 tuned to transmit on the frequency to Which are tuned sync signal receivers El), located at the teleinetric transmitting stations of the system. The specific structure and 'mode of operation of the sync signal generating equipment provided at the receiving and recording station of the present system forms no part of the invention, it being sufficient that signals be provided which are ci suitable character tococperate with the synchronizing and framing equipment 93 at the various telemetric transmitters, to assure that the motors l will maintain precise framing and synchronization vlith respect to the motor t5. Many such synchronizing and framing systems are available in the prior art, and l do not desire to be restricted to any particular one of such systems. have, however, specified one specific system which I prefer to employ, a full description ci Which, both in respect to structure and rhode of operation,V is to he found in `Letters Patent of the United States, No. 2,263,541, to Nicholson.

A further signal which may be utilized for synchronizing in the present system, as has been lorieiiy indicated hereinefore, is the omni-directional beacon system of the type approved by Civil Aeronautics Authority for installation generally at airports, This system operates by transmitting a rotating pattern of energy and a fixed pattern of omni-directional energy, the speed. of rotation of the rotating pattern being related in frequency to a modulation frequency of 30 cycles per second, impressed on the omni-directional transmission. The 30 cycle signal provides a convenient synchronizing signal, and may be employed to drive all the synchronous motors l and 35 of the present system at identical speeds. Suitable framing signals may be superimposed on the 30 cycle modulation.

Suffice it to state that while various synchronizing and framing systems may be utilized in conjunction with the present system, as above indicated, I do not consider the use of any speciiic such system to be essential, and the various systems suggested are intended for purposes of exempliiication only.

By virtue of the dentical framing and rotative speed ofthe recorder motor 35 and of the telemetric transmitter motors 1, a common zero of time may be provided for all the equipment of the present system, and the coil supporting arms 8a as well as the helical platen 33 may so be arranged that upon passage of the coils 9 adjaent a meter position corresponding with zero value of the measured quantity, or of zero angular displacement of the meter pointer 4, the helical platen 33 shall be so phased as to be potentially able to create a mark on the record receiving surface 34 at a point corresponding with a zero calibration .line entecedently provided on the surface. The record receiving surface may be calibrated laterally, bymeans `cf laterally spaced, parallel lines 40., provided thereon (see Figure 3) to enabledetermination ofthe value of any mark created on .the paper. The total lateral dimension, of the record. receiving surface 34, .or any predetermined portion thereof, ymay be caused lto :correspond with :the total .possible angular .dis- ,placement of .theV pointer y4 of .the aneroid cell 3 .and :the tot-al altitude range of the system.

it will be recalled that :the transmit-ter l .per- .forms its primary function as an interrogator yoi Tan interrogator-responsor `or, distance measuring equipment. vThe responsorl ofthe .distance ,measuring equipment comprises a .receiver 1.3 which is normally inoperative, but Whichis :keyed to icperative condition instantaneously -i-n response to the-outputiof a multivibrator or separe -wave generator M., operation of which .is initia- -teddn response to r:each l.transmitted pulse, :the @Square wavegen-erator,operating `toprcvide a sensitizing or..g2.ri1l .control voltage to the .receiver V; 3 soonafter ,application thereto of .the control .pulse .sderived from the. ,.nulser. 2. .rbrator .is :ofthe .type well.. known, per .sa which .maintains .its ..condition, once it has been Iestabvlished, until. a .further control pulse is applied thereto,.,at:which.time ,it .returns .to `its original position. In the V.present application .the pulseds applied to .theimulftiyibrator .|14 from the receiver. I3 itself, .in responsel yto a received or transponded nu1se ,.and in fthe .oi. position the Asensitivityof the receiverisagain ,reduced :to a low value It ,will thus be evident that `time, .gatvingeis xapplied tothe receiver lg3, which is .effectivelysvvitched .on inrespcnse `to each transmittedgpu'lsearrd off in .response to each received .:pulse,.;cemaining thereafter `in 1oli Y position until .the occurrence Lof .a further transmitted pulse. '.Thereceiver b3 ana-vbo .irenderedinoperative dur- .ing transmission by ,transmitter :l in accordance vwith .known techniques.

VThe time ybetween .successive pulses :is ,chosen :to be largein relation :to the .time lofpropagation .ofelectro @magnetic energy ;for the :maximum intended range ofithefequipment by a :factor of theorder of 110.0350 .milden that :there is `eifect ias-time sharing as between various aircraftfof the .system for4 range measuring purposes.

.Rangeatany one aircraft mayfbemeasured in termstof the motaloperating ltime @of thema-itivibrator 14, which in turnldeterrnines .the average A`these gcurrentspr voltages vbeing measurable by means of 'a voltmeter yor ammeter to .determine .range for .-distance.

.'.Ilhe specific character of the distance Ameasuring equipmentI utilized in my invention is per se .well knownandissubject tomodiiication in defor an "illustration of the appearance of a'record as provided by the apparatus ofthe invention, Vas so fardescribed. The arrow labelled time repres/ents,thejlongitlldinal direction of "feed of rec- .Illd receiving ,surface j3'4iwth time, the jlines '60 The multividisclosed and described 110 and -Gvl representing time krecords of aircraft altitude.

It will be realized that the rtransrnitting equipments built in accordance with the present invention transmit atmospheric pressure, rather than true altitude, so that for a given altitude from the various aircraft of the system may vary from day to day or from hour to hour, in accordance with the value or ambient pressure temporarily existing in a given area. To overcome this difficulty, `the calibration provided on the record receiving surmay be provided under control .of the value of local atmospheric pressure existing on the ground. There is thereby `.provided an automatic correction for variations in local atmospheric pressure, since the value of each altitude sure. The pulse transmitter 23 synchronizes a Yfrequency multiplying oscillator .ofy the multivibrator type 29, which provides a number of equally spaced, f nl, Y therein. Thel pulses provided `vrby the multi-vibrator are so spaced that lwhen aping .surface ,3 4', the pulse frequency `of the multivibrator 29 being :fixed and the ,pulse separation being properly chosen for Ithat purpose. phasing or time positioning of :the pulses .are determined, however, by ,thee pulse timing roi' the `pulse output of the transmitter 28, the latter .being determined in .part b y local atmospheric conditions, the calibrationlines varying in lateral position on the surface 34, all simultaneously, in accordance with such conditions. Examples of suitable calibration lines 49 are provided in Figure 3, the position of .the lines with respect to the edges of the surface 34 being of .-signicance primarily in determining'the existence of variations of atmospheric pressure from standard conditions.

`In accordance with the systemof :the .present invention, all the aircraft as well yas the ground station, may utilize aneroid altimeters pre-fcalibrated for standard atmospheric conditions, k.and ycorrect; vreadings :of altitude .-.will Ibe various recording stations, or .at the `same recording station at various times, without introducing altitude corrections into eters .on the various aircraft.

To this point the system disclosed corresponds in general with that `disclosed in my co-:pending application, entitled Altitude and Distance Recorder, led concurrently herewith. The respect rin which the present application ,distinguishes now be described, including the :apparatus utilized for adding t0 the altitude .representativerecords indications ,of azimuthend range, as Well as apreferred manner f ofgidentif-y- Sing the various records and :relatingsameito the `originating craft.

The various altitude lines recorded at the Vrecording station, andieach Voriginating from a distinct aircraft, maybe'identified, A'ina :preferred manner, by l*periodically retarding .or advancing, v`or both, in coded sequence, V'the :time positions of pulses transmitted ffor lrepresentation ther .altimpulses, which produces over suitable brushes.

il of altitudes, or by interrupting ltransmissions in coded sequence. Since each aircraft utilizing the present system may be provided with a distinct coding sequence individual to that craft, the altitude records may be each identified in terms of the originating craft.

As still a further, and extremely valuable function, the altitude representative records may be further modulated in a manner significant of the values of measurable quantities, in addition to altitude. This function may be accomplished by utilizing the time scale inherently provided by the longitudinal feed of record receiving surface 34, as a scale of measurement against which may be compared the positions oi" one or more pointers. Specifically I synchronize the movement of the surface 34 with the movement oi' one or more space scanning members, which scan the locus of positions of one or more pointers, the position of each pointer being representative of a measured value or quantity. Upon concurrence or coincidence o the positions of a scanning member with a pointer position, a modulation of the altitude representative transmission is effected, which causes a corresponding modulation of the altitude representat've record at the recording station. l prefer to modulate the altitude representative transmission by retarding or advancing temporarily the time positions of the transmitted a corresponding deviation in the altitude record.

By examining any altitude representative record, and'observing the location and character or lateral deviations thereof, the values of the telemetric `quantities which are transmitted as supplementary to altitude may be determined. That these quantities'may be azimuth and range has lbeen suggested hereinbefore, but it will be clear that the values of any desired quantities may be substituted for the suggested quantities, without departing from the scope of the invention.

Referring again to Figure arm 8a, which supports for rotary motion the pick-up coil 3 is provided with two further pickup coils Se and 3b, the former of which is advanced slightly in phase position with respect to coil 9, and the latter of whichis retarded slightly in phase position with respect to coil il. The magnet e is made of sufcient length to provide magnetic flux linkages with all of coils 3, 9a and 9b, or alternativelyT is supplemented by additional magnets 6a and 6b, positioned on the same radius as is magnet 6, for such purpose. One terminal of each of coils 9c and 9b is connected in common to a grounded slip ring 40. The remaining terminals of coils 3, 9a and 9b respectively are connected with slip rings il, lla, and Hb respectively, which are electrically coupled to leads l l, i I a and 4 lb respectively, The leads 4l, 41a and Mb are connected with contacts 42, 42a and 42h of a three position selective switch, having a selector arm 43, which is electrically connected with pulser 2.

' The position 'of selector arm .43 determines which one of coils S, 9a and'gb shall be connected with pulser 2 to determine the time positions of pulses transmitted byA transmitter i, coil 9 being the coil normally so connected for transmission of altitude representative signals. ing coils 9a or 8b for coil 9, it is possible to advance slightly or to retard slightly, the normal time positions of altitude representative pulses, a

fact which is utilized for transmitting telemetric ,signals supplementary to thealtitude representative signals.

1 of the drawings, thev By substitut- The selection of contact points 42, 42a, 42h by switch arm 43 is accomplished by means of electro-magnets 44 and 45, the former of which, when energized pulls arm 43 into contact with point da, and the latter of which pulls arm 43 into contact with point 42D. When magnets 44 and 45 are both de-energized, the arm 43 remains in contact with switch point 42.

Upon temporary connection of coil 9a in circuit with pulser 2, in response to operation of relay 44, a slight lead or advance in timing is introduced into the altitude representative pulses, and upon temporary connection of coil 9b in circuit with pulser 2, in response to operation of relay 45, a slight delay or retardation is introduced into the ltiming of the altitude representative pulses as provided in response to signals generated in coil il. Upon consideration of the structure and mode of operation of the recording device of Figure 2 of the drawings, it will be evidentthat corresponding slight deviations of altitude representative recorded lines, may be caused to occur in the record provided by the recorder R.

Referring to Figure 3, wherein is illustrated in plan View, a longitudinally extending portion of thev record receiving surface 34, there is shown a pair of discrete altitude representative records e0 and Si, which may be interpreted by comparison with altitude calibration lines 40, to provide a time record of altitudes of each of a pair of aircraft. Laterally deviated portions of line til, denoted 63 and til, are shown to illustrate responses, respectively, of the recorder R to transient energization of magnets 44 and 45, deviation td representing a transient advance of pulse timing and deviation 63 a transient retardation of pulse timing. it is intended that the `timing of deviations t3 and t4, respectively, as

represented by their longitudinal positions, on surface 34, with respect to an arbitrary starting or reference line S5, hall represent the values of measurable quantities, which in the presently preferred embodiment and application of the in'- vention, may correspond with the range and azimuthal bearing of the transm`tter l with respect to a ground located beacon system (not shown).

An initial or zero reference line or starting position 65 may be impressed on the record receivingl surface 34 by applying to the marker element 3i at definite times, and hence at definite space intervals on the surface, a recording potential of duration equal to one or several scanning cycles of helical platen 33. To provide zero reference lines t5 at definite positions on the surface 34 and also at definitely spaced time intervals, I secure to the drive means 65 for the take up roll el of the record receiving surface 34 a timing vcam et, which operates for each complete rotation of take up roll El to close a circuit maker and breaker t8 the latter serving, when closed, to energize a sync pulse generator G9. The latter provides recording signal to marker element 3l over leads ttc and teli, of sufficient duration to enforce a line, as E5, completely across the surface 34.

lThe cam te maybe driven quite slowly, say at one revolution in each 30 seconds, which may correspond withthree inches of paper feed, in presently conventional facsimile recorders. I may obviously utilize basic time intervals which are shorter or longer than 30 seconds, if desired, the latter being merely one example of a convenient value, which will be utilized in what follows, for the sake of convenience. The signal impulses provided by generator $9 may be of' square wave,

while shaft Bia is normally driven by shaft 8| at the same rate of speed as the latter, the possibility exists of displacing shaft Bia rotatively with respect to shaft for framing purposes. To the shaft Bia is secured a hollow cone |02, the axis |03 of which is not in alignment with the shaft 0 la, but departs from such alignment by an angle of perhaps A further shaft |04 is provided, which is hollow and co-axial with the shaft Bia, but is of relatively short length. The shaft |04 has secured thereto a hollow cone |05, adapted to mesh with the cone |02 and the axis of which |03' makes the identical angle with respect to shaft |00 that exists between the axis |00 of cone |02 and the axis of shaft Sla. The shaft |04 is arranged to be irrotatable, but to be translatable along the shaft 0m, and is further arranged to have its inner conical surface |00 normally out of contact with the outer conical surface |01 of the cone |05 by a sufiicient distance, to assure that during a full rotation of cone |02 no contact exists between it and cone |05 despite the relatively great eccentricity existing between axis |03 and to axis i03 during most of the rotation of shaft Sic.

Surrounding the hollow shaft |00 is a solenoid |08, and secured to the shaft |00 is an annular ring of magnetic material |09, which may be attracted by solenoid |08 when the latter is energized, thus to translate shaft |00 to the left, as

seen in Figure fi, and causing meshing of cones |02 and |05.

rlhe solenoid pulses derived from the sync pulser |00 is energized in response to 60 (Figure 2),

such pulses occurring oncel in each seconds.

The cones |02 and |05 are adapted to mesh completely in only one relative angular position thereof, and the outer surface |01 of cone |05 and the inner surface |06 of cone |02 are vmade sufficiently smooth and frictionless so that if in response to actuation by solenoid |08 the cone |05 is driven internally of cone |02 and into contact therewith, while the cones |02 and |05 are not in the said one angular position, a camming action occurs, the :friction clutch |0| slipping, and the cone |02 rotating until it is in complete mesh with cone |05. i

rEhe cones 02 and |05 are initially aligned relatively to one another, and to the position of the arm 02, so that in the position of complete mesh the arm 00 is in the proper angular relation for initiation of a cycle of scan of the locus of possible positions of the pointer 82.

ln normal operation only very slight camming action is required in response to each zero-setting or framing action of the apparatus, since drive 80 may be depended on to have but very slight, if any, angular drift in the time required for a single revolution of shaft Bia. Upon initiating operation of an airborne equipment, or after a temporary interruption of operation thereof, however, the shaft 0m may be at random position, and a considerable camming action may be required to zero set same. Since the camming action endures only during reception of sync pulses, there may be available insufficient camming time to accomplish complete framing in a single operation. This in itself is not serious, since framing may take place in a plurality of steps, without detriment except to the accuracy of the first few telemetric transmissions. The blocks 90 represent mechanisms responsive to the output of receiver 00 for zero-setting the scanning arms 82, 82', and since two distinct framing ,operations are required in the present system,

one for framing synchronous motor l, and another for framing or zero-setting scanning arms 82, the receiver 20 is provided with suitable circuits (not shown) for detecting and separating the different signals, distinguishable in terms of their frequencies, and originating in sync signal generators 30 and 00o, respectively, and 'for applying the different signals to the proper framing mechanisms, 00 and 00 respectively.

The apparatus as described hereinbefore requires one additional desirable element, that is, a means of identifying each aircraft of the system with' a particular record. To accomplish this I utilize a pair of metallic code wheels 20,0 and 20|, which are permanently grounded, and which comprise circumferential raised portions 202 and 203, respectively. The wheels 200 and 20| are driven from a common drive shaft 204, actuated by a clock mechanism 205. The clock 205 drives the wheels 200 and 20| at a rate of approximately, but not precisely, one revolution in each thirty seconds, so that rotation of clock 205 is not quite synchronized with that of drive 00. The peripheral raised portions 002 and 203, on wheels 200 and 20i respectively, extend circumferentially for but a few degrees of aro, and are mutually interrelated in accordance with an arbitrary coded'sequence, which is peculiar to the transmitting aircraft. A pair of brushes 204 and 205 are provided which are normally out of contact with wheels 202 and 200, but which are so located that upon passage of projections 202 and 203 under brushes 20d or 205 respectively, contact is made, grounding leads 00 or 0l', as the case may be, and thereby energizing relay 44 or 05, as the case may he, in a coded sequence, determined by the spacing and character of the projections 202 and 203. The spacing and character of projections 202 and 200 may be individual to each of the telemetric transmitters of the system, and hence may identify the associated aircraft, the energizations of relays 40 and 05 in coded sequence providing like coded deviations of the altitude line specific to the transmitting aircraft. Reference numeral 20? (Figure 3) denotes the character of one aircraft identiiying record, as provided by the invention.

It will be clear, since the characters of range and azimuth representative recordings are similar to the characters of identification recordings, that confusion between the two may on rare occasions arise by reason of coincidence of records having different signincances. Such occurrences will be rare, however, and non-repetitive due to the lack of synchronisin between the rate at which identifying signals are provided and that at which range and azimuth representative signals are provided.

As an alternative method of aircraft identication I may provide a clock driven cam 200, which cams open in coded sequence a circuit maker and breaker 200, located in series with the lead 2|0, which connects the selective switch arm 43 with puiser 2. When the alternative method of coding transmissions is utilized the various records provided on record receiving surface 30 may be identified in terms of coded breaks 20h?l in the record line. Identification representative interruptions of transmission may be provided at relatively long intervals, to minimize interference with telemetric transmissions.

The invention, further, may be applied to uses other than telemetric recording of altitude, range and bearing, by replacing the aneroid cell 3 and the specific meters and 90', or any one of them,

quantity.

- with; devicesvforfmeas-uring ctherqnanuues than altitude; range and bearing, respectively.

accordingly;l while' Iy have' described; and illustmtecr one specific embodiment of my invention, asY required by` the pertinent statutes relating tot patents ofjthe.; United. States, it will beV clear tlrperscnsskill'ed'inY the telemetric arts that various uses may be foundv for the invention, and that variousA4 modifications' of the: general' arrangement disclosed, as well as of various detailsthereof, may beA resorted towithout: departing from the: true spirit' and'scope ofthe invention; as defined in the appended claims.

Whatv I claimand. desire to secu-re: by' Letters Patent ofi the 'United States: is z' 1;.In combination, a transmitter` of discrete pulses-means for modulating the timing of: said pulses* in accordance with the value of a. iirst measurable" quantity, and7 means for further modulating the timing of selected ones'ofl said pt rl'ses,V selection: being' accomplished in* accordanceA with the. value of a further measurable 22AV telemetricf recording' system. comprising means for transmitting pulses having' pulse time positions characteristic representative of the valuevof' a first measurable-'quantity and means for modifying saidpulse time positions at intervals-timed; in accordance with the values of afurther-measurable lquantity;

3;. A telemetric system comprisinga transmitter for transmitting av carrier, means foraugmenting theimagfnitude of said'- carrier at time positions determined-1l by the` value".` of' a; rstV measurable quantity; andmeansifor'varying said time positions'` at times-representative of furtherfmeasurabl-e quantity.

4. A telemetric system ina'ccordance with claim 3 and further comprising rarecorder lhaving perithe value of a -odicfline scanning marking means and a time fed.f record receiving surface; meansV for synchronizing'said line scanningVl means with said means for augmenting, means for actuating said recorder tofcreatefmarks-'on said-,record receiving -surface with operation of said means for varying.

M5; Az telemetric` system comprisingmeans for transmitting-af pulsedA carrier" having a distinguishable characteristic representative of the valuevof a first measurable quantity, and means for modul-ating said' distinguishable characteris- Avalue-of`said^second'measurable quantity.

6. A' tel-emetric system comprising a transmit- "ter for transmitting carrier modulated I at `times spondingzwith thetime posifi i) having a positionablepcinter, means for measarable quantity, and

'repetitive equal time cally repetitive equal riod-ically time position modulating said transmitter in? accordance with altitude of' an elevated object, means for further time position modulating said transmitter periodically at predetermined times ina further and diiTerent time cycle, and means for determining said predetermined times in accordance with the value of a; measurable quantity.

8. The combination in accordance with claim 7 wherein said measurable quantity is a navigational parameter associated with said elevated object;

9.. In combination, a pulse transmitter having pulse time position modulating means, means for controlling said modulating means in accordance with the value of a for varyingthe pulse measurable quantity, means time positions of pulses controlled by said means for controlling, a meter scanning arange of positions of said pointer for discovery of the position of said pointer, and means responsive. to discovery of` the position of said pointer for actuating said means for varying.

10. The combination in accordance with claim 9 and further comprising a recorder having a laterally line scanning marker and a longitudinally time fed record receiving strip, means for synchronizing the time feed of said strip With the scanning action of said means for scanning a range of positions, and means responsive to said transmitted signals for actuating said marker at positions laterally of saidY record'receiving surface corresponding with pulsetime positions oftransmitted pulses.

l1. .In combination, a pulse time position modulated transmitter, means for controlling the pulse time positions of pulses' transmitted byv said transmitter in accordance with the value of a means for temporarily modifying the time' positions o'f said transmitted pulses atrtimes, representative of the value of a further measurable Iquantity.

12. The combination in accordance with claim 11 wherein said" means for modifying comprises means for selectively retarding and advancing said times representative of the valueV of a further measurable quantity.

13. The combination in accordance with claim 1l and further comprising av recorder for recording time; positions of said transmitted pulses.

14. The combination in'accordancewith claim 13 wherein said recorder'compri'ses a time fed record.V receiving surface calibrated to enable interpretation of time positions of said transmitted pulses and of times of modification of time positions of said transmitted pulses.

15. In combination', a pulse generator, means comprising` an, altimeter for establishing time positions of pulse generation of said pulse generator with respectto predetermined periodically intervals, meansk comprising a range measuringv device' for establishing further single time pcsitionsiwith respect to each of further and different predetermined perioditime intervals, and means for further 'modulating said pulse generator only Vduringsaid further time positions.

- further time position modulating said pulses' at times within said second periodic equal time intervals determined in accordance with the value of a second predetermined quantity.

17. In combination, a pulse generator, means for establishing iirst periodic timing intervals, means for establishing second periodic timing intervals, said first and second periodic timing intervals being unequal, means for establishing rst pulse time positions within said first periodic timing intervals, means for establishing second and third pulse time positions Within said second periodic timing intervals, means for actuating said pulse generator for generating pulses during said iirst pulse time positions, and means for differently further modulating the timing of the generated pulses' during each of said second and third pulse time positions respectively.

18. In combination, a pulse generator, means for establishing rst periodic timing intervals, means for establishing second periodic timing intervals, said iirst and second timing intervals being unequal, means for establishing first pulse time positions Within said rst periodic timing intervals, means for establishing second pulse time positions within said second periodic timing intervals, means for activating said pulse generator for generating pulses during said first pulse time positions, and means for modulating the timing of the generated pulse only during said second pulse time positions.

19. In combination in a telemetric system, a plurality of relatively remote stations, means for establishing first periodic timing intervals for all said stations, means for establishing second relatively remote timing intervals for all said stations, said iirst and second timing intervals being unequal, means for establishing first pulse time positions Within said first periodic timing intervals independently at each of said stations, means for establishing second pulse time positions within said second periodic timing intervals independently at each of said stations, a pulse generator at each of said stations, means for activating said pulse generators at each station for generating pulsesvduring said first pulse time positions at that station, means for modulating the timing of the pulses generated at each station only during the second pulse time positions at the station, and means for commonly receiving and visually indicating the time positions of all said generated pulses with respect to both said .first and second periodic timing interva s.

20. In combination, a pulse generator, means comprising an altimeter for establishing time positions of pulse generation With respect to predetermined periodically repetitive equal time intervals, means comprising a bearing measuring device for establishing further time positions With respect to further and different predetermined periodically repetitive equal time intervals, and means for further modulating the output of said pulse generator only during said further time positions.

21. In combination, a pulse generator, means comprising an altimeter for establishing time positions of pulse generation with respect to predetermined periodically repetitive equal time intervals, means comprising a range measuring device for establishing further time positions with respect to further and different predetermined periodically repetitive equal time intervals', means comprising a bearing determining ldevice for establishing further time positions with respect to said further and different predetermined periodically repetitive equal time intervals, and means for further distinguishably modulating the output of said pulse generator during said respective further time positions.

22. In combination, means for transmitting periodic pulses, means for establishing first periodic time intervals, means for establishing second periodic time intervals, means for determining the time positions of said periodic pulses with respect to said first periodic time intervals, means for deviating said time positions of said periodic pulses at predetermined time positions with respect to said second periodic time intervals, a visual indicator having means for establishing visual indications having positions simultaneously with respect to a pair of coordinates, and means responsive to said. periodic pulses for controlling said visual indicator to provide an indication of the time positions of said pulses with respectto said first and second periodic time intervals simultaneously in terms of positions of said visual indications with respect to both said coordinates.

23. In combination, a remote source of first synchronizing signal, a remote source of second synchronizing signal, local means responsive to said rst synchronizing signal for establishing first periodic time intervals, local means responsive to said source of second synchronizing signal for establishing second periodic time intervals, means for generating pulses having predetermined time positions with respect to said first periodic time intervals, and means for modifying said pulses at predetermined time positions with respect to said second periodic time intervals. Y

24. The combination in accordance with claim 23 wherein is further provided a visual indicating station comprising a marker and a record receiver, means for establishing relative motion between said marker and said record receiver in two coordinate directions in response to said iirst and second synchronizing signals respectively, and means responsive to said pulses for activating said marker to create a visual indication.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 1,928,969 Kuffel Oct. 3, 1933 2,125,491 Dean Aug. 2, 1938 2,252,083 Luck Aug. 1`21, 1941 2,378,604 Wallace June 19, 1945 2,380,520 Hassler July 31, 1945 2,396,955 Lange Mar. 19, 1946 2,400,828 Keinath May 21,1946 2,403,603 Korn July 9, 1946 2,404,571 Finch July 23, 1946 2,418,836 Hawes Apr. 15,- 1947 2,419,292 Shepard Apr. 22, 1947 2,468,045 Deloraine Apr. 26, 1949 2,504,126 Howe Apr. 18, 1950 2,521,881 Suomi Sept. 12, 1950 2,524,832 Poylo Oct. l0, 1950 2,535,107

Wallace Dec. 26, 1950 OTHER REFERENCES Fidelman, Electronic Applications in Meteorology, in Radio News, Engineering'4 Dept. May 1946. pages 36-38. 

